Fuel injection pump for internal combustion engines



Dec. 15, 1964 c. KbsTER FUEL. INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Filed Oct. 4, 1962 fiwz-w rap CLA (/5 K05 TE R United States Patent ()filice 3,161,138 Patented Dec, 15, 1964 8 Claims. .(rii. [103,-41

The present invention relates to a fuelinjeetion pump for internal combustion engines comprising two pistons which are radially and coaxially arranged in a rotating pump body and which can be moved forward and backward in a common pump operating space as afunction of a non-rotating cam ring. The pistons are adapted to open a return-passagefor terminating their effective compression stroke. I

In conventional-injection pumps of this type each of the two pistons opens a return passage thus effecting a connection between the pump operating space and the return passage, which connection serves for terminating the effective compression stroke. Since ordinary manufacturing processes do not allow to obtain a simultaneous opening of the return passage by the two pistons of the pump, the opening is effected step-by-step and consequently does not result in the required rapid increase of the opened crossseotion. Hence, the cross-section opened during one unit of time at the beginning of the opening process is as a rule only half as large as it would be if the return passage were simultaneously opened by both the pistons of the pump. This is disadvantageous in regard to a desirable rapid termination of the injection process.

It is the object of the present invention to obtain a constant rapid increase in the cross-section of the return passage opened by the pistons of the pump irrespective of unavoidable manufacturing tolerances.

This object is attained according to the invention by telescoping the pistons of the pump andby providing them with cooperating sections of a return passage being common to both pistons.

It is another object of the present invention to increase the speed of the opening process to twice that attained for each of the individual pistons inconventional injection pumps.

In the arrangement according to the invention the increase of the opened cross-section is ashigh per unit of time as in conventional injection pumps where the two pistons of the pump open the return passage simultaneously. However, in practice thiscan be attained only in exceptional cases.

The invention will be more fully appreciated upon reference to the accompanying description and the following drawings, wherein FIGURE 1 is a partly schematic cross-section along line I -I in FIGURE 2, and

FIGURE 2 is a partly schematic cross-section along line II-II in FIGURE 1.

Referring now to the drawings more in detail, wherein like reference numerals indicate like parts, a shaft 3 being disc-shaped in its central section which is serving as a pump body 4 is supported in the casing of a fuel injection pump for a four-cylinder internal combustion engine. The casing consists of pants 1 and 2. Parallel to the axis of the shaft 3, two longitudinal grooves 5 are positioned in the pump body 4, diametrically opposed with respect to h other, andserving tcrguid ng the roll ra Whose rolls 7 cooperate with the surface 8 of a cam ring 9 inserted into part 1 of the casing and being stationary therein. The cam surface -8 is provided with four cams 10.

The roll rams 6 actuate two telescoped pistons 12 and 13 of the pump. The exterior piston 13 is guided as tightly as possible in a transverse bore 14, which bore ends in the longitudinal grooves 5. The interior piston 12 fits as tightly as possible into the exterior piston 13. Positioned between the two pistons is the pump operating space 15. Connected with the latter is an axial bore 16 in the piston 12 and a radial bore 17 in the piston 13. Radial bores 18 originating from an annular groove 19 in the skirt surface of the interior piston end in the axial bore 16 of the interior piston 12. The radial bore 17 of the exterior piston 13 is in permanent connection with an annular groove 20 which is provided in the shaft 3 concentrically to the guide bore 14 for the piston 13. The annular groove 20 is also connected with an axial bore 22 in the shaft 3. Four radial bores 24 branch off from the bore 22 which is closed to the exterior by means of a stopper 23. The radial bores 24 are staggeredly arranged by 90 with respect to each other in a cross-sec- ,tional plane of the shaft andcooperate withan inlet conduit 25 originating from an inlet aperture 26 in pant 2 of the casing. Furthermore, branching off from the axial bore 22 is a radial distributor bore 27 which cooperates with four outlet channels 28 in part 2 of the casing. Only one of these outlet channels 28 which are also arranged at an angular distance of 90 with respect to each other,

is illustrated in the drawing. Each outlet channel 28 ends in an outlet aperture 29 which is'connected to aconduit 30 leading to an injection nozzle 31.

A radial bore 33 in the exterior piston 13 cooperates with the annular groove 19 in the interior piston 12. The bore 33 originates from an annular groove 34 which is provided in the skirt surface of the exterior piston 13 and is in constant connection with an annular groove 36 in part 1 of the casing by means of an inclined bore 35 in the shaft 3. Said annular groove 36 is connected wtih the aperture 38 of a return passage by means of a bore 37.

A fuel pump 40 conveys fuel from a tank 41 via a filter 42 through a conduit 43 to the inlet aperture 26 provided in part 2 of the casing of the pump. Connected to the aperture 38 of the return passage provided in part 1 of the casing of the pump is a conduit 44 leading via a backpressure valve 45 to the tank 41. Between the transfer pump 40 and the filter 42 a non-return valve 46 is connected to the conduit 43. The discharge side of the valve 46 is connected to that section of the conduit 44 which is directly connected with the tank 41.

The described injection pump operates in the following way:

Proceeding from the end position of the suction stroke of the pistons 12 and 13 of the pump as illustrated, the pistons are urged to the interior upon further rotation of the shaft 3 and camming of the rolls 7 on the earns 10. The pistons of the pump thereby expel from the working space 15 of the pump the fuel flown in during the pre vious suction stroke under the pressure of the fuel pump 40, whereby the fuel is urged through the bore 17, the annular groove 20 and the axial bore 22 into the distributor bore 27 which conducts the fuel to one of the outlet channels 28 and via the outlet aperture 29 and the conduit 30 to the nozzle 31. The effective compression stroke and thereby the transportation of the fuclto the nozzle as well as the injection process are terminated as soon as the angular groove 19 and the bore 33, forming the cooperating portions of the return passage common to the pistons 12 and 13 of the pump, meet in the course of their oppositely directed movement. The fuel that is still expelled from the operating space 15 of the pump flows via the bores 16 and 18, the annular groove 19, the bore 33 and the annular groove 34 to the inclined bore 35 and from the latter through the annular groove 36, the bore 37, the aperture 38 of the return passage and the conduit 44 into the tank 41. The back-pressure valve 45 mounted in conduit 44 prevents the emptying of the conduits within the injection pump, which conduits have been filled by the return fuel.

As soon as the rolls 7 have reached the peak of the cams 10, the compression stroke of the pistons 12 and 13 of the pump is terminated and the suction stroke of said pistons begins. During the rotating movement of the shaft 3 one of the radial bores 24 is moved into connection with the inlet channel 25. Thereafter the fuel that is sucked out by the transfer pump from tank 41 and pressed through the conduit 43 into the inlet aperture 26, flows through the bores 25, 24 and 22, the annular groove 20 and the bore 17 into the operating space 15 of the pump. Under the pressure of the introduced fuel the pistons 12 and 13 of the pump move outwardly, thereby maintaining the rolls 7 in contact with the surface 8 of the cam ring 9. As has already been explained, the oppositely directed movement of the pistons 12 and 13 of the pump allows for the opening of the return passage, which opening is effected by means of the annular groove 19 and the bore 33 at a speed resulting from the sum of the speeds of the two pistons. Thereby a very rapid opening of the return passage and consequently a rapid termination of the injection process is attained.

For the purpose of varying the quantity of fuel supplied to the internal combustion engine, a throttle slider 25' can be mounted in the inlet conduit 25, as illustrated by the dash-dotted line in FIGURE 1.

It will be understood that this invention is susceptible to further modification and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. In a fuel injection pump for internal combustion engines having a casing consisting of a first and a second part, fuel inlet conduits, fuel outlet conduits, a shaft rotatably mounted in said casing and a stationary cam ring disposed in the casing and having a plurality of camming surface portions cooperating with roll means, the combination comprising a central section in said shaft which is rotatable therewith, said central section forming a pump body, an interior and an exterior piston in radial and coaxial arrangement, said pistons being slidably disposed in said pump body, a pump operating space between said pistons, said roll means comprising a roll ram and roll each fixed to the ends of said pistons, said rolls being adapted to cam on the surface portions of said stationary cam ring upon rotation of said shaft and actuate said pistons, bore means in the interior piston and bore means in the exterior piston, and return passage means leading from said pistons through said casing and being connected back to said fuel inlet means, said bore means being adapted to be brought in opening connection with said return passage, thereby allowing fuel to return from said pump operating space through said return passage out of said casing.

2. In a fuel injection pump for internal combustion engines having a casing consisting of a first and a second part, fuel inlet conduits, fuel outlet conduits, a shaft rotatably mounted in said casing and a stationary cam ring disposed in the casing and having a plurality of camming surface portions cooperating with roll means, the combination comprising a central section in said shaft which is rotatable therewith, said central section forming a pump body, an interior and an exterior piston in radial and coaxial arrangement, said pistons being slidably disposed in said pump body, and each of said pistons having a piston skirt, a pump operating space between said pistons, said roll means comprising a roll ram and roll each fixed to the ends of said pistons, said rolls being adapted to cam on the surface portions of said stationary cam ring upon rotation of said shaft and actuate said pistons, an axial bore and radial bores in said interior piston, said radial bores leading from said axial bore through the skirt of said interior piston, a radial bore and annular groove means in the skirt of the exterior piston, an inclined bore in said shaft, said inclined bore having its upper opening in connection with said annular groove means, an annular groove in the first part of said casing, said annular groove surrounding the lower opening of said inclined bore, a conduit leading from said annular groove toward the outside of said casing and a return passage opening at the outside of said casing, said return passage opening being connected with said conduit, said bores, groove means, inclined bore, annular groove and return passage opening forming a return passage from said pump operating space, thereby allowing fuel to return from said pump operating space through said return passage out of said casing.

3. A fuel injection pump as claimed in claim 2, wherein an annular groove in the skirt of said interior piston is provided into which said radial bores through the skirt extend.

4. A fuel injection pump as claimed in claim 2 further having a throttle slider disposed in said fuel inlet conduits.

5. In a fuel injection pump for internal combustion engines having a casing, fuel inlet conduits, fuel outlet conduits, a shaft rotatably mounted in said casing and a stationary cam ring disposed in the casing and having a plurality of camming surface portions, the combination comprising a section in said shaft which is rotatable therewith, said section forming a pump body, an interior and an exterior piston in radial and coaxial arrangement, said pistons being slidably disposed in said pump body, a pump operating space between said pistons, said pistons being actuated upon rotation of said shaft, bore means in the interior piston and bore means in the exterior piston, and return passage means leading from said pistons, said bore means being adapted to be brought in opening connection with said return passage.

6. A fuel injection pump as claimed in claim 5, wherein an annular groove is provided in the skirt of said interior piston, into which groove said radial bore through the skirt extends.

7. In a fuel injection pump for internal combustion engines having a casing, fuel inlet conduits, fuel outlet conduits, a shaft rotatably mounted in said casing and a stationary cam ring disposed in the casing and having a plurality of camming surface portions, the combination comprising a section in said shaft which is rotatable therewith, said section forming a pump body, an interior and an exterior piston in radial and coaxial arrangement, said pistons being slidably disposed in said pump body, and each of said pistons having a piston skirt, a pump operating space between said pistons, said pistons being actuated upon rotation of said shaft, an axial bore and a radial bore in said interior piston, said radial bore leading from said axial bore through the skirt of said interior piston, and a radial bore and annular groove means in the skirt of the exterior piston, said bores and groove means forming a return passage from said pump operating space.

8. A fuel injection pump as claimed in claim 7, wherein an annular groove is provided in the skirt of said interior piston, into which groove said radial bore through the skirt extends.

(References on following page) 5 References Cited by the Examiner UNITED STATES PATENTS 2,004,161 6/35 Fausel 103-463 2,918,872 12/59 Nicolls 103154 5 2,946,292 7/60 Chmielecki 103-460 5 FOREIGN PATENTS 684,901 7/30 France.

JOSEPH H. BRANSON, IR., Examiner.

LAURENCE V. EFNER, Primary Examiner. 

1. IN A FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES HAVING A CASING CONSISTING OF A FIRST AND A SECOND PART, FUEL INLET CONDUITS, FUEL OUTLET CONDUITS, A SHAFT ROTATABLY MOUNTED IN SAID CASING AND A STATIONARY CAM RING DISPOSED IN THE CASING AND HAVING A PLURALITY OF CAMMING SURFACE PORTIONS COOPERATING WITH ROLL MEANS, THE COMBINATION COMPRISING A CENTRAL SECTION IN SAID SHAFT WHICH IS ROTATABLE THEREWITH, SAID CENTRAL SECTION FORMING A PUMP BODY, AN INTERIOR AND AN EXTERIOR PISTON IN RADIAL AND COAXIAL ARRANGEMENT, SAID PISTONS BEING SLIDABLY DISPOSED IN SAID PUMP BODY, A PUMP OPERATING SPACE BETWEEN SAID PISTONS, SAID ROLL MEANS COMPRISING A ROLL RAM AND ROLL EACH FIXED TO THE ENDS OF SAID PISTONS, SAID ROLLS BEING ADAPTED TO CAM ON THE SURFACE PORTIONS OF SAID STATIONARY CAM RING UPON ROTATION OF SAID SHAFT AND ACTUATE SAID PISTONS, BORE MEANS IN THE INTERIOR PISTON AND BORE MEANS IN THE EXTERIOR PISTON, AND RETURN PASSAGE MEANS LEADING FROM SAID PISTONS THROUGH SAID CASING AND BEING CONNECTED BACK TO SAID FUEL INLET MEANS, SAID BORE MEANS BEING ADAPTED TO BE BROUGHT IN OPENING CONNECTION WITH SAID RETURN PASSAGE, THEREBY ALLOWING FUEL TO RETURN FROM SAID PUMP OPERATING SPACE THROUGH SAID RETURN PASSAGE OUT OF SAID CASING. 